Parsing JSON to do math? - arrays

Question

I'm new to programming (especially JSON format), so please forgive me not for using proper terminology :)
Using Python 3.7 Requests module, I receive a JSON response. To keep things simple, I made an example:
{
"Bob":
{
"Age": "15",
"LastExamGrade": "45",
},
"Jack":
{
"Age": "16",
"LastExamGrade": "58",
}
}
What I would like to do is parse the JSON responses to extract two items from each response/structure and save it to a list like this (I think this is called a tuple of tuples?):
[("Bob","45"),("Jack","58")]
Then, after receiving doing this, I will receive another similar response, such as the following (where the only thing that changed is the exam grade):
{
"Bob":
{
"Age": "15",
"LastExamGrade": "54",
},
"Jack":
{
"Age": "16",
"LastExamGrade": "70",
}
}
I want to also save the name and grade into a tuple of tuples (list).
Lastly, I would like to subtract the first exam score of each person from their last exam score, and save this into a final list, which includes the name, final exam grade, and grade improvement, like this:
[("Bob","54","9"),("Jack","67","12")]
What is the simplest way to do this using Python 3? As for my own research, I've searched all throughout StackOverflow, but couldn't find out how to parse a JSON like mine (For example, in mine, the name is outside of the curly braces), and had difficulty doing math operations for JSON items.

Answer 1

I'd recommend using a dedicated package for calculations like pandas:
first_exam_grades = pd.DataFrame.from_dict(first_exam_results, orient='index').astype(int)
second_exam_grades = pd.DataFrame.from_dict(second_exam_results, orient='index').astype(int)
improvements = second_exam_grades.LastExamGrade.to_frame()
improvements['Improvement'] = second_exam_grades.LastExamGrade - first_exam_grades.LastExamGrade
This will give you something that looks like this:
Now you can output it anyway you'd like
list(zip(*([improvements.index.tolist()] + [improvements[c].values.tolist() for c in improvements])))
This will give you [('Bob', 54, 9), ('Jack', 70, 12)] as you want.

Answer 2

One possible solution, using coroutines. Coroutine receive_message holds up to last two values LastExamGrade from the message for each student and produces list of student name, last grade and improvement over last grade:
json_messages = [
# 1st message:
{
"Bob":
{
"Age": "15",
"LastExamGrade": "45",
},
"Jack":
{
"Age": "16",
"LastExamGrade": "58",
}
},
# 2nd message
{
"Bob":
{
"Age": "15",
"LastExamGrade": "54",
},
"Jack":
{
"Age": "16",
"LastExamGrade": "70",
}
},
# 3nd message (optional)
{
"Bob":
{
"Age": "15",
"LastExamGrade": "14",
},
"Jack":
{
"Age": "16",
"LastExamGrade": "20",
}
}
]
def receive_message():
d, message = {}, (yield)
while True:
for k, v in message.items():
d.setdefault(k, []).append(v['LastExamGrade'])
d[k] = d[k][-2:] # store max last two messages
message = yield [(k, *tuple(v if len(v)==1 else [v[1], str(int(v[1])-int(v[0]))])) for k, v in d.items()]
receiver = receive_message()
next(receiver) # prime coroutine
for msg in json_messages:
print(receiver.send(msg))
Prints:
[('Bob', '45'), ('Jack', '58')]
[('Bob', '54', '9'), ('Jack', '70', '12')]
[('Bob', '14', '-40'), ('Jack', '20', '-50')]